Copper coating



Patented Nov. 12, 1929 UNITED STATES PATENT OFFICE JOSEPH G. DELY, OF NEW YORK, N. Y., ASSIGNOR T CHEMICAL RESEARCH 80 DESIGN- ING' CORPORATION, OF NEW YORK, N. Y., A. CORPORATION OF NEW YORK Ho Drawing.

apply the copper to t COPPER COATING- The invention relates to the art of coating metallic materials such as steel or iron plates with an adherent outer layer composed of metallic copper. The object of the invention is to produce a relatively continuous or tim perioi ate layer of copper and to produce improved results over those obtained by known processes.

lln one oil the known methods of copper coating it has been proposed to mix a line copper-bearing substance with heavy OllS or the like to produce a viscous, paint-like substance which is then applied to rolled iron plates by printing rolls. The plates are then plates are pickled dilute sulfuric acid to i'emove the scale. The cleansed plates are rolled again and then become the finished product. @opper coating of plates thus made, while being apparently continuous, is in effect exceedingly porous with the result that the iron foundation is readily attachable and that the life of the plates in consequence is relatively short.

I have now discovered that the cause of the defect in this process is that the copper particles do not weld together in the baking step to any substantial degree, but merely form a superficial network spaced apart by every large number of minute openings. Th1s result, I find, is due to the fact that the atmosphere in the baking oven, although ordinar ly regarded as a neutral or reducing agent, will, at the high temperatures in the baking oven, act as an oxidizing agent for metallic copper and thereby impede and/or obstruct welding together ofthe copper particles. The gases in the bakin oven, when produced by the composition 0 natural gas, (a preferred fuel) contain steam and carbon dioxide and relatively little carbon monoxide. The cracking products of the oil used to make the initial paint-like mixture also inhibit the fusion of the copper. In order to glve the copper particles, an opportunity of welding together under conditions which will cleanse the coperparticles and revent their oxidation, I discard the use, in t e first place, of oils or hydrocarbons in makin the initial mixture, but

he iron plates in associabaked at high temperatures. (hi cooling, the

Application filed April 19, 1928. Serial No. 271,411.

tion with material containing a substance such as sodium fluoride. Sodium fluoride is preferred, but sodium chloride or a mixture of sodium fluoride and sodium chloride may also 1 be used. a

D A formula suitable for use in this connection may contain 4 grams oi sodium fluoride with gram of borazr and 1 0. c. silicate of soda (40 as The foregoing iormula is computed with relationto 5 grams of copco per in powdered form and, of course, suthcient water to give proper consistency. If the cop per powder is mixed in at the outset, the re sultant thick paste can be applied to the iron plates by means of printing rolls, but for cercs tam purposes an operator n first dip the iron plates into a bath containin the sodium halide, borax, and silicate of so a, the powdered copper being subsequently applied in appropriate quantity. Tron lates coated with a composition of the descri ed type will, when baked at high temperatures, have a sun face of molten material within which the copper particles are not only cleansed, but pro tected against oxidatioufand within which F5 the copper particles may have a relative movement in settling against the iron surface and against each other, the molten slag tending to float upon the surface of the settled copper particles. The molten material thus 0 oll ers protection from the time that the copper is first exposed to the possibility of attack by the gaseous environment existing in the heating chamber. The copper particles under the protective influence setforththen become welded to the iron foundation and to each other, forming a copper surface which, compared with the copper surfaces produced. by the prior art "fusion method, presents relatively large areas of truly continuous coating free from perforations or pin holes. The sodium fluoride and sodium chloride slags are readily removable by ickling in dilute sulfuric acid. The slags of the boraxsilicate of soda vehicle, if not accompanied by a halide of sodium, would be exceedingly dlflicult to remove. r

The essential characteristics of the materials to be employed in accordance with my invention in connection with the fusing of copper particles upon the surface of a metallic object of ferrous character are that they must supply a body within which the copper particles may he completely enveloped as fusion progresses and such protection mustbe offered from the time that the copper, but for l e protective coating, would begin to be subject to attach the atmosphere prevailing the heating chamer; that the locdy must operate as cleanser for the copper particles; fuse temperature lower than copper and have a lower surface tension with respect to copper than copper has for copper or for ferrous material, and that the slag must be easily removable, These various requirements are satisfied pre-eminently by the use of a horas-silicate of soda vehicle containing a sodium halide and preferably sodium fluoride.

After the pickling operation, the coated plates produced by my process are preferably washed in the usual manner to remove the pickling fluid and loose particles of slag, and the plates are then given a final rolling treatmcnt,

if the process is carried out with the addition of stannous oxide in the surfacing material the result will be a copper coating of the bronze types whose color would depend on the amount of the added tin material and any such modifications are intended to be included within the scope of my claims.

I claim:

1. The process of coating a metallic object with copper which comprises applying a coat to the object, said coat containing a halide of sodium and an inorganic vehicle of the silicate type for said halide and copper articles, and subjecting the thus prepared ob] cot to a hightemperature baking operation, whereby the copper particles are welded to each other and to the surface of said object in the form of relative large areas of substantially imperforate copper.

2. The process of coating a metallic object with copper which comprises preparing an aqueous mixture of a non-carbonaceous fusible character containing inorganic material including a slagging agent and a halide of a member of the alkali family and copper particles, coating the metallic object with the material constituting said mixture, heating a chamber to a high temperature by the combustion of a gaseous fuel, passing the products of combustion through the chamber, exposing the coated metallic object to the high temperature existing in the said chamber to weld the copper to the surface of the object, and to itself, so as to constitute, on the object, a relatively large area of a substantially inn, perforate adherent copper coating. I

3. The process of coatinga metallic object of ferrous character with copper which comprises preparing an aqueous pooliof a non-- carbonaceous character containing a halide of weapon sodium, borer, silicate of soda, and a co perbearing material, passing the metallic o ject through said pool to wet the surfaces of said object with the material in the bath, producing a high temperature in a chamber by the combustion of natural gas, maintaining the metallic object in the said chamber under the influence of the high temperature for a duration sufficiently long to weld the copper to the surface of the to itself and to cause the formation a molten la er of material containing the aforesaid sodium, borax, and silicate of so tects the copper while undergo from oxidation, and cooling the or 1, j set to cause solidification of layer of coating material. a

a The process of coating a ferrous object with copper which comprises surfacing the object with a slagging material of non-carbonaceous, fusible character containing sodium fluoride and fine particles of copper, heating the thus surfaced object to temperatures in the neighborhood of the melting point of copper an atmosphere produced by the combustion of a fuel, and removing the resultant slag, while leaving the copper as a welded layer.

5. The process of coating a ferrous object. with copper which comprises surfacing the object with fine particles of copper in a mix ture of borax, sodium silicate, and sodium halide material containing sodium fluoride, heating the thus surfaced object to temperatures in the neighborhood of the meltin point of copper in an atmosphere produce by the combustion of a fuel, and removing the resultant slag while leaving the copper as a welded layer.

6. The process of coating 2. sheet of ferrous materialwith copper which comprises applying an aqueous mixture containing sodium fluoride, sodium chloride,borax, sodium silicate, and copper to the sheet, passing the coated sheet through a chamber heated to a high temperature by the combustion of natural gas, to cause a welding together of the copper and of the copper to the ferrous sheet in the form of relatively large areas of substantially imperforate copper while protecting the welding copper against oxidizin influenccs by the fused mixture of the so ium '1 chloride, sodium fluoride, borax, and sodium silicate, cooling the sheet of ferrous material, 7 pickling the cooled sheet in dilute acid to remove scale from the surface of the sheet, cleansinglthe sheet of said acid and scale, and rolling t e sheet to present a smooth copper surface. In testimony whereof I have hereunto set my hand,

JOSEPH G. DELY. 

